TY - JOUR

T1 - Particle image velocimetry measurements of massively separated turbulent flows with rotation

AU - Visscher, Jan

AU - Andersson, Helge I.

N1 - Funding Information: The assistance of Dr. Joël Sommeria and Dr. Henri Didelle (LEGI, Grenoble) and Dr. Mustafa Barri (NTNU, Trondheim) is appreciated. Professor J. P. Johnston (Standford University) kindly sent us the tabulated reattachment-length data included in Figure . The work reported in this publication was supported by the European Community’s Sixth Framework Programme through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB III, Contract no. 022441 (RII3), and by the Research Council of Norway through a research grant Contract no. 171725/V30.

PY - 2011/7/27

Y1 - 2011/7/27

N2 - Measurements of instantaneous velocity fields in the separated flow downstream of a backward-facing step in a rotating channel are presented for the first time. Particle image velocimetry (PIV) measurements were made for 13 different rotation numbers Ro at a bulk flow Reynolds number of about 5600. The expansion ratio 2:1 was the same as in the flow visualization study by Rothe and Johnston [ASME J. Fluids Eng. 101, 117 (1979)] which covered about the same range of Ro. The measured mean flow pattern exhibited substantial variations with the rate of system rotation. In particular, the length of the primary separation bubble decreased monotonically with increasing anti-cyclonic rotation and increased with increasing rate of cyclonic rotation, in keeping with the earlier observations. At the highest anti-cyclonic rotation rate, the flow field also separated from the planar wall where the shear layer flow was subjected to cyclonic rotation. The PIV data for the in-plane components of the Reynolds stress tensor were severely affected by the imposed system rotation. Almost all the striking affects of the Coriolis force observed herein could be explained by means of the exact production terms in the transport equation for the second-moments of the velocity fluctuations. These changes were in turn consistent with the observed alterations of the mean flow field.

AB - Measurements of instantaneous velocity fields in the separated flow downstream of a backward-facing step in a rotating channel are presented for the first time. Particle image velocimetry (PIV) measurements were made for 13 different rotation numbers Ro at a bulk flow Reynolds number of about 5600. The expansion ratio 2:1 was the same as in the flow visualization study by Rothe and Johnston [ASME J. Fluids Eng. 101, 117 (1979)] which covered about the same range of Ro. The measured mean flow pattern exhibited substantial variations with the rate of system rotation. In particular, the length of the primary separation bubble decreased monotonically with increasing anti-cyclonic rotation and increased with increasing rate of cyclonic rotation, in keeping with the earlier observations. At the highest anti-cyclonic rotation rate, the flow field also separated from the planar wall where the shear layer flow was subjected to cyclonic rotation. The PIV data for the in-plane components of the Reynolds stress tensor were severely affected by the imposed system rotation. Almost all the striking affects of the Coriolis force observed herein could be explained by means of the exact production terms in the transport equation for the second-moments of the velocity fluctuations. These changes were in turn consistent with the observed alterations of the mean flow field.

UR - http://www.scopus.com/inward/record.url?scp=79960929235&partnerID=8YFLogxK

U2 - 10.1063/1.3599702

DO - 10.1063/1.3599702

M3 - Article

AN - SCOPUS:79960929235

VL - 23

JO - Physics of fluids

JF - Physics of fluids

SN - 1070-6631

IS - 7

M1 - 075108

ER -